SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0228 AM CDT Fri Oct 09 2020

Valid 111200Z - 121200Z


Isolated strong to severe thunderstorms may occur Sunday across
parts of the northern Plains into the Upper Midwest, with marginally
severe thunderstorms also possible across parts of the Southeast.

...Northern Plains/Upper Midwest...
A large-scale upper trough over western Canada and the northern
Rockies should further amplify on Sunday across parts of the
northern Plains while gradually acquiring a negative tilt by Sunday
night. At the surface, a strong cold front is forecast to sweep
east-southeastward from the northern/central Plains into the Upper
Midwest through the period in tandem with the amplifying upper
trough. Limited low-level moisture return is expected ahead of this
advancing cold front, and a low-level inversion may inhibit
convective development along the front through much of the day.
Still, some potential for storms remains evident from parts of far
eastern ND/SD into MN and perhaps parts of IA late Sunday afternoon
and continuing into the evening. Strong deep-layer shear will be
present across this region, which may act to organize any storms
that can develop and subsequently grow upscale along the cold front.
Isolated severe wind gusts will probably be the main threat through
Sunday evening given a mainly linear mode expected, although some
large hail may also occur early in the convective life cycle given
the presence of steep mid-level lapse rates. Storms should weaken
with eastward extent across the Upper Midwest late Sunday as they
outrun the modest forecast instability.

The remnants of Delta are forecast to move northeastward across
parts of the TN Valley on Sunday. Modestly enhanced mid-level
south-southwesterly winds will remain across parts of the Southeast
as a surface warm front lifts slowly northward across parts of the
Carolinas. There appears to be enough veering/strengthening of winds
with height to support modestly organized storms across the warm
sector, with weak to locally moderate instability also forecast.
Isolated strong/gusty winds appear to be the main threat, although a
brief tornado cannot be ruled out.

..Gleason.. 10/09/2020

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